DC-DC Converter Load Current Measurement Circuit
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Solution Overview
Problem
Existing methods for measuring load circuit current consumption are either costly and power-intensive or fail to accurately track power consumption due to architectural distinctions affecting the relationship between current consumption and switching frequency, and often require disconnecting the load from the power supply, which reduces voltage regulation quality.
Innovation Solution
The implementation of load current measurement circuits that scale the peak inductor current of a DC-DC converter to produce a capacitor charging current, adjusting based on converter operating mode, frequency, and peak current, using a coulomb counting approach with scaling circuitry, current sources, switching circuitry, and a comparator to accurately measure current consumption without adding significant cost or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods for measuring load circuit current consumption are used, then measurement capability is provided, but cost and power consumption increase significantly
Solution Approach 1:
The metering circuit uses the existing inductor current from the DC-DC converter to charge the capacitor, rather than requiring an external power source. The inductor current itself serves as the charging current, making the measurement system self-powered and eliminating additional power consumption.
Solution Approach 2:
The inductor in the DC-DC converter serves dual purposes: it performs its primary function of energy storage and transfer, and simultaneously provides the charging current for the capacitor in the metering circuit. This multi-functionality eliminates the need for separate measurement power sources.
2Measurement precision
If existing measurement methods are implemented, then current measurement is achieved, but device complexity and cost increase
Solution Approach 1:
The metering circuit is integrated with the existing DC-DC converter circuitry. The capacitor is charged from the inductor current that already flows in the converter, and the comparator uses the existing output voltage. This merging eliminates the need for separate, complex measurement systems.
Solution Approach 2:
The capacitor serves as an intermediary element that accumulates charge from the inductor current over time. By measuring the time required to charge the capacitor to a threshold voltage, the circuit indirectly measures the average load current without requiring direct current sensing components.
3Measurement precision
If load disconnection is used for measurement, then current measurement is possible, but voltage regulation quality deteriorates
Solution Approach 1:
The capacitor is charged continuously from the inductor current during normal operation, before any measurement action is taken. The measurement is performed by observing when the capacitor voltage reaches a threshold, without requiring interruption of the load connection or power supply.
Solution Approach 2:
The charging of the capacitor from the inductor current occurs continuously during the entire operation of the DC-DC converter. The measurement process does not interrupt this continuous charging action, allowing the load to remain connected and voltage regulation to be maintained throughout the measurement process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides accurate load current measurement while minimizing additional cost and power consumption, maintaining high voltage regulation quality by measuring current consumption based on charge-discharge timing and peak current applied to the inductor, effectively addressing the limitations of existing methods.
Implementation Method 1
The capacitor is coupled to the current source. The switching circuitry is configured to switchably connect the current source to the capacitor
Implementation Method 2
The comparator is coupled to the capacitor. The comparator is configured to generate a signal indicating that a voltage across the capacitor exceeds a threshold voltage
Data Source
AI summary
A switch-mode power supply includes a DC-DC converter and metering circuitry that is coupled to the DC-DC converter. The metering circuitry includes scaling circuitry, a current source, a capacitor, switching circuitry, and a comparator. The scaling circuitry is configured to generate a reference current scaled to be a predetermined fraction of a peak current flowing in an inductor of the DC-DC converter. The current source is configured to output a first current that is one-half of the reference current. The capacitor is coupled to the current source. The switching circuitry is configured to switchably connect the current source to the capacitor. The comparator is coupled to the capacitor. The comparator is configured to generate a signal indicating that a voltage across the capacitor exceeds a threshold voltage.